The present invention concerns metallating crystalline olefin polymers which have polymerized therein a minor amount of at least one nonconjugated diene. More specifically, the present invention concerns a process for metallating crystalline, ethylene polymers having polymerized therein a minor amount of at least one nonconjugated diene monomer and, optionally, a minor amount of at least one 1-olefin monomer. The present invention also concerns graft polymers and functionalized polymers prepared from such metallated polymers.
The term "metallation", used in its broadest sense, describes a substitution reaction in which a non-carbon atom is replaced by an alkali metal atom. In a narrower sense, it is believed that metallation of unsaturated polymers occurs by allyl hydrogen exchange whereby an anion is produced. The resulting anion is stabilized by delocalization with the adjacent double bond. The alkali metal atom is suitably provided by an organo-alkali metal compound such as an alkyllithium compound.
Metallation of conjugated diene polymers with an organolithium compound, such as n-butyllithium, in combination with either a tertiary diamine, such as, tetramethylethylenediamine (hereinafter "TMEDA")or a potassium alkoxide, such as potassium-tert-butoxide or potassium-tert-amyloxide, is known. See, e.g., A. F. Halasa et al., "Metallation of Unsaturated Polymers by Using Activated Organolithium Compounds and the Formation of Graft Polymers II", Journal of Polymer Science, Volume 14, pages 497-506 (1976).
E. W. Duck et al, in U.S. Pat. No. 3,703,566, disclose metallation of unsaturated hydrocarbon elastomers and formation of graft copolymers by polymerizing one or more monomers in the presence of the metallated elastomer. The elastomer has polymerized therein ethylene, a 1-olefin such as propylene, and a nonconjugated diene monomer and is more commonly known as an "EPDM terpolymer". Metallation is accomplished by admixing a solution of the terpolymer in an inert organic solvent with a complex of an alkali metal hydrocarbon, such as n-butyllithium, and a polar compound, such as a tertiary diamine or an alkali metal alkoxide.
Metallation of unsaturated hydrocarbon elastomers is commonly conducted in solution to attain enhanced levels of metallation efficiency. Care must be taken, however, in selection of the solvent. Metallation in nonpolar organic solvents, for example, leads to an undesirable rise in solution viscosity due to ionic association.
It would be desirable if olefin polymers could be metallated so as to minimize viscosity increase without sacrificing either degree of metallation or polymer solids content. This would allow for simpler agitated reactor design with reduced agitation energy requirements and for greater amounts of polymer solids per reactor volume.
It would also be desirable if there were available a process for metallating crystalline olefin polymers which are not soluble in the common organic polar solvents used to metallate hydrocarbon elastomers. Polymers fitting this description include those having polymerized therein a minor amount of nonconjugated diene monomer. One such polymer is a crystalline ethylene/nonconjugated diene polymer. Another such polymer is a crystalline ethylene/nonconjugated diene/1-olefin polymer.